Centrifugal separator



V. W. MECHSAAC CENTRIFUGAL SEPARATOR Filed March 2l, 19.30 4 SheetsMSneet l ATTORNEY Oct. 11, 1932.

V. w. MaGlSAAC CENTRIFUGAL SEPARATOR Filed March 21. 1930 4 sneetsK-sheet 2 F/G. E.

NVE/V707@ -fi m Trop/w94 oct. 1'1, 1932. v. w. Mms/mc 1,882,389

CENTRIFUGAL SEPARATOR Filed March 2l, 1930` 4 Sheets-Sheet 4 Patented Oct. 11', 1932 s UNITED STATES wget-*1.1 w,

PAT-ENT `OFFICE VERNON WESLEY MACISAAC, OF MONTREAL, QUEBEC,` CANADA cnN'ritirUGAL 'snrAnA'ron Application filed` March 21,71930. Serial No. 437,754.

The invention relates to a centrifugal separator as described in the present specificati on and illustrated in the accompanying drawings' that form part of the same.

, rlhe invention consistsv essentially of the novel features of construction pointed out broadly and specifically in the claims for novelty whereby the progress of the material into, through and out of the bowl is facilitated.

The objects of the invention are to segrew certain heavier niaterialsfroni the main body fed and deposit it in. pockets, thus relieving the machine from time to time during l5 the operation as well as removing lighter ini-Y purites continuously, thereby `effecting a great saving in time and labor and insuring greater' efficiency; to promote the separation in an unique manner of heavy and. light impurities from fibrous pulps such as paper stock and from non-fibrous pulps such as fluid suspensions of mineral particles and the classication thereof by centrifugal sedimentation; to avoid interruptions caused by com- A paratively frequent stoppages for removal of l. ,ment and reduce the liability of picking up impurities in the outward flow of presumab y pure liquid pulp to regulate the rotation of the rotary members in order that the con- ;iu stant or intermittent progression of the heavier iaterial will readily accumulate the material in the pockets, from which it is readily accessible for removal; to facilitate the mechancal operation of the machine parts by :sa contributing to maintenance' of motion through the recovery of energy at the ldiccharge; and generally to provide in centrifu- O'al separating machines a construction that will lend itself to the furthering of the sepa- 'i ration and the scavenging of' the machine i; efficiency throughout.

while in motion through relievingthe machine of heavier and lighter reclaimableY or waste material and that will effect economy in the consumption of power and increased Y In the drawings, Figurel is a vertical sectional view of a form of centrifugal machine adapted to various purposes showing a means of discharging heavier material during rotation.

y. D0 Figure 2 is a cross sectional view on the line 2%-2fin Figure 1. Y* Figure 3 is a cross line 3-3 in Figure 1.

Figure 4 is a de sectional -vievvv on the y tail of a valve and stem.A Figure 'V5 is a detail of another form of valve. andstem, such asV shown in Figure 6. Figure 6 is a vertical sectional view. of a modified form yofloowl showing ,another arrangement'of pockets and valves and a means of recovering power. Y

Figure 7 is a cross ysectional view ontheline 7-7 in'Figure 6. ,u

Figure 8 is an exterior view showing the inner shell Vand' spiral scraper in thel form .ofl the invention illustrated in Figure l.

Like numerals of reference indicate correspondingparts in the various figures. Y

In the separation of solids from liquids, heavier liquids from lighter .liquids and any hea-vier materialv from lighter materials, the use ofthe4 centrifugal machine is widely known, therefore modern developments'have largely to do with the shape of the bowl, the progression of the materials, the discharge and disposition of the separated material and .the operation ofthe bowl to effect the .sepaadaptation 'of means for vthe reduction in power.

Referring to the drawings, and particularly to the invention as illustrated in Figure l, the bowl is of frusto-conical shape being cylindrical at the inlet end y16 and bell shaped outwardly from said inlet end, as indicated by the tapering portion 17 within which the sedimentation occurs.

The bell shaped portion 17 of the bowl flares outwardly at the extreme outward end 18 and is flanged at 19.

The cover 2O is anged at the outer edge 21 and forms with said flare an annular recess 22-fro1n the inner side.

The cover is rigidly secured to the bowl, being bolted thereto through the iianges and the said recess is a depository for the sedimentation that is eventually worked up Vfrom the inlet end of the bowl.

A number of pockets 23 extend outwardly from the recess 22 at intervals around the bowl and these pockets have the relief openings 24.

The cover 2O is formed with the central discharge opening 25xencircling the main shaft 1 26, and this opening 25 is restricted in relation to the diameter of the bowl at the narrowest portion thereof, that is to say, the diameter'of the opening 25 is considerably less than the diameter of the cylindrical end ofthe bowl, and it is over the edgel of this 'opening 25 that the discharge occurs, this discharge taking place along the plane, indi- 'cated by the arrows PV-P.

It is to be noted that the diameter of the discharge opening determines the annular depth of the liquidwithin the bowl,as centrifugal forces acting on the bowl and its contents tend to force the liquid into a` ring against the wall of therbowl, and maintain an approximately cylindrical inner diameter n of liquid Vabout equal to the diameter'of the Vdischarge opening 25.

Because of the predominance of centrifugal forces over that of natural gravity (-ordinarily-being'from 300 to 500 times gravity) the liquid will be maintained with an inner diameter approximating the inner diameter of the discharge opening, whether themachine is operated with the bowl and shaft v26 and containing the inlet passa-ge 29 encircling the shaft 26, therouter wall of the inlet being joined to the hub proper b y they radial arms 30, said outer wall having the annular flange Slithrough which the bowl 15 is suitably bolted to the outer hub wall.

The main shaft 26 is suitably mounted and ldriven and is encircledby the tubular mounting or sleeve shaft 32 extending in thelighter sleeve shaft 34 projecting loosely through the hub 28 beyond the bowl at the inlet end.

The shell 35 is secured to the radial arms 30 and is flanged inwardly at the outer end 36 and at the inner end 37, thus the shell being securely fastened to the radial arms .may rotate with the shaft 26 or rotate freely there.

on, that is to say, the sleeve shaft 32 may be f through which the subsided particles mustpass being of great importance in the functioning of centrifugal machines, as well as making it possible to reduce the outlet diam.

eter and to effect a saving in the consumption of power.

The sleeve shaft 32 is rotatably mounted on the bush nut 38 screwed on to the shaft 26 thereby affording lendwise adjustment for the sleeve shaft and consequently for the shell and regulating-the thickness of the layer of liquid being treated between the shell and the bowl. Y

The Y outwardly flaring portion or bell shape of the bowl l5 tends to permit particles subsided on the inner surface of said bowl to move more readily towards the recess 22 or :c

collector channelk giving them in effect a Si l down hill motion which is preferably assisted by Scrapers'. K

rlhe flexible scraper stripV 39 is loosely woundwithin the bowl l5 andv secured at its ends to the rotating shell thus forming a spiral scraper resting on the inner surface of the bowl, so thatthe said scraper will rotate at a slower angular velocity than the bowl, and thus will move the particles forwardly and outwardly towards the collector channel or recess 22 being a backward rotation induced principally byv the negative torque, of acceleration of iniiowingliquid n emanating from the acceleration dished plate 40 or deflector as it may be called.

VThis acceleration plate 4() is of circular form and dished and rigidly secured to the bottom of theinner radial extension from the sleeve shaft 32, the vanes l1 extending voutwardly from the disc centre l2 and 'projecting from the dished wall 43, consequently as the liquid enters the inlet 29 it flows on to the dished wall i3 nearto thepdisc centre 42 from which it spreads on to the dished wall 4:3 between the vanes 41 and in thus entering, the liquid flowing on to the plate l0 has a distinct influence on the speed of the shell besides aecelerating the flow in the carryin g out of the centrifugal action. Y

It is to be noted that this speeding up or acceleration of the incoming liquid can only be performed at the expenditure of considerable energy and by powerful reaction on the vanes 41 and that in such machines a large portion of the power is consumed in so accelerating the continually inflowing liquid so thata strongly resistive torque opposing rotation is imparted to acceleration member 40 and thence to 32, 30, 35 and 39 when Vit is rotating (as it is constrained to do) at a speed nearly equal to that of the bowl l5.

This feature is to be noted particularly in that it is used in a unique manner to supply speed control of the inner parts in relation to the bowl, principally within the bowl rather than principally through external gearing and provides the whole or a principal part of the torque required to backwardly rotate scraper members in relation to the outer bowl, thereby making the regulation of said differential speeds easy of accomplishment with small and cheap differential gearmg apparatus.

The speed control for the shell outside of the bowl is in the form of very simple differential gear mechanism in which the internal gear 44 is rigidly mounted on the sleeve sha-ft extension 34, and this internal gear coacts with the spur gear 45.V

The internal gear 46 is keyed to the main shaft 26 and in position'opposes the internal gear 44. l

The spur gear 47 coacts with the internal gear 46 and the two spur-gears 45 and 47 are fixedly mounted on a common shaft 48, this shaft 48 being journalled in the fulcrum member 49, rotatably mounted and supported on the internal gear 46, this rotation of the fulcrum Vmember 49 on the internal gear 46 being controlled by the friction of the brake band 50, suitably arranged for opera-tion in any conventional manner.

The ratio of the gear 45 to the gear 44 differs slightly from the ratio of the gear 47 to the gear 46, so that if the member 49 is fixedly held from rotation by the brake band 50, the moti-on of the main shaft 26 through the gear 46 will permit the gear 44 to travel only at a dierent angular speed from the shaft 26, as fixed by the gear ratios built into the mechanism, hence the shell 35 will rotate at a different angular speed from the shaft 26 and the bowl.

The partial release of the brake will per-v mit the fulcrum member' 49 to travel about with the internal gear 46, assuming frictional resistances within the mechanism are so balanced as to permit this, but at a less speed f: than the internal gear 46, so that the difference of speed beween the shaft 26 and the shaft 32 will bev lessened as the speed of the fulcrum member approaches that of the in- Y ternal gear, and when the brake band is sufli- Vciently released so that the fulcruminember passages 5l which aremade through turbine blades or divisions 52 in an annular row adj acent to the edge of the central discharge opening.

This formation from the inner wall surface of the cover 2O is between the'inner wall surface and the rin 53, and constitutes an inner recoveryturine feature introduced in the path lof the outiiowing liquid.

This liquid flows around the edge of the opening and through the passage 54 between the turbine blades or divisions .55 closed in by the ring 56 and constituting the outside rei covery turbine feature in the path of the discharge, thus considerable energy is recovered from the outflow of the liquid.

The skimmer 5.7 extends from the underside of the ring 53, around the mouthof the passages v54 leaving sucient space for the ingress of the thinner liquid to outside turbine, and this skimmer, which may be in sections forming spouts or a complete ring, or in any other shape which rwill accomplish the '55?'. -i

purpose, separates the froth or foam containing light impurities or reclaimable matter and directs them overand beyond the outer wall of the ring 56.

A. ball valve 58 in each of the-pockets 23Y e seats on the outlets 24 and the stems 59 extend from the ball valve .5,8 through to the roclrer arms 60, being pivotally secured to said valves and rocker arms.

. These stems' 59 extend through the skimgi,.-

mer or between spouts forming the skimmer to the rocker arms 60, which are pivotally secured to the hub 27. The collar 6l is slidably mounted on the shaft 26, and has the flaring inner end 62 forming a cam face engaging the inwardly offset sections 63 of the rocher arms 60, said offset sections 63 being preferablyv centrifugally balanced by the weights 64 in the direction of the collar 61.

The sliding collar 61 operates just-as many rockerarms as there happen to be valves to correspond to the number of pockets and these stems and valves and rockers are arranged to balance one another. The sliding collar carries a pin 65 extending inwardly in a corresponding slot 66 in the shaft 26 and the pins 65 engage the operating rod 67 which is slidably arranged in the centre of the shaft 26; As to whether this rod is operated manually or automatically is` entirely Cri a matter of' choice for the manufacturer or constructor.

The intake 68 is connected by the tubular extension 69 to the source of material to be separated, and extends to formv the annular intake chamber 7'0 which empties into the inlet 29 at 7l, through which it reaches the interior of the bowl l5.

The inner shell' is preferably of light material and is supported from its tubular mounting as explained and as this mounting extends into thediiferential gear mechanism the tubular mounting or sleeve shaft 32 willv rotate on its journalling on the bush nut at the desired speed.

The actual shell 35 terminates at the inner end in the inwardly extending flange 37 and at the outer end in the inwardly extending flange 36, the flange 86 projecting slightly beyond the edge of the discharge opening.

he accelerator plate 4i() may pass beyond the flange 37 and leave a narrow opening 7 2 between itself and the flange 37 through which foam may pass carrying the light impurities or particles within the shell.

At the outer end of. the shell, the drag links or pushers 73 are flexibly secured to said shell and the sweeper ends 74 of these drags are in proximity to the inturned flange of the head 20, consequently in rotation these pockets 78 in an annular recess 79V intermediate of the length of the bowl 7 5, said pockets havingthe relief openings 8O and the ball valves 8l closing said openings.

Theball valves 8l are supported and operated by the stems 82 pivotally secured thereto'and secured to the sliding collar 88 mounted on the main shaft 76.

The collar 83 is connected by the rods 85 to the slidable sleeve-86 which is. operated 'tij-,r collar87 the particular operating gear being here omitted as any rod gear or lever can be used. l Y

rllie bowl 75 extends beyond the flange 7 7 and flaresoutwardly and it is recessed from YVthe inner side at the discharge end to form the Yslide valves 90 which are pivotally connected i through the stems'9l to the sleeve 86, therefore when the sleeve 86 is operated both the ball Valve and slide valve are removed from the relief openings, so that the heavier mate# rial isY expelled from the bowl duringthe rotary movement. l

to the maintenance ofthe momentum of the bowl during rotation.

The bowl may be driven by a primary turbine member 96 introduced inthe path of the feed of material to the bowl, this primary turbine member 96 having the directing blades 97 forming passages leading to the impact face members 98 which are impinged by the liqui d in its ow under pressure. l

The inner deflecting shell 99 is mounted on the shaft 76 by suitable khub and arms and may or may not rotate independently of the bowl 75. This shell limits the depth of the liquid progressing towards thedischarge and alsov carries drag links or pushers 100 sweeping the solids into the pockets 78 and spiral flexible scraper 102 and has holes 103 to permit liquid to enter said shell'.v

The pockets 88 have their entrance openings in the direct passage of the liquid along the wall, so in that portion of the machine it may not be necessary to have any pushing 'or scraping means for sweeping the solids into the pockets though this may be provided if it is `found desirable.

ln the operation of thisinvention, the material is fedin to one end, and inthe preferable -form of the machine comes in contact with the acceleration and distributing membeil lOl at the bottom ofthe inner shell.

In the beginning, he great body ofliquid is held to the depth determined by the central opening in the head, thus the inner level of this hollow column of liquid partially fills the shell, usuallywith a light waste liquid which remains dead behind the light shell, thus stabilizing it by a constant wall of liquid.

The reduction of the speed of the shell by carrying forward he Scrapers, facilitates the progress of heavier material which eventuallyV fresh liquid by the drags or pushers to `fill the pockets, which are relieved at intervals by the Vmovement of the sliding sleeve, through the opening of the relief openings by tie removal of the valvesY operated by Athe stems and rocker arms connected. to said sleeve.

The treated liquid continues flowing outwardly and passes through the inside recovery turbine impinofing on the blades or divisions and on behind the skimmeninto the outer recovery turbine where it is directed into delivery passages by centrifugal force. i

The skimmer cuts off the lfoam or froth which passes the outside of the inside recovery turbine and this froth is eventually dissipated or reclaimed according to the particular separation which is being accomplished. In the modified form of the invention, the operation is so nearly the same and hardly requires description, as the liquid passing along the wall of the bowl reaches a depthdetermined by the inner shell and intermediate inwardly projecting flange, thus the heavier material is caught by the intermediate pockets and the same pushing effect is accomplished by the shell below said flange.

The operation is continued above the flange and the lighter liquid passes behind the skimmer while floating foam or froth discharges over the skimmer.

Ihe heavier material outside the flange is caught in pockets at the end of the casing and there relieved. Practically the same arrangement of valve operation is shown in the modified form of the invention, but the recovery turbine is at the rim ofthe outer casing, and

f. this recovery turbine forms the outlet for the lighter material which in the manufacture of pulp is the liquid relieved from the heavier impurities and from the lighter impurities, but it is obvious that the machine may be used for separating other materials.

What I claim is l. In a centrifugal separator, a rotary bowl and shaft mounting therefor, an inner shell having upper and lower inwardly extending flanges and a tubular shaft mounting journalled on said shaft and supporting the shell and a spiral flexible strip attached to said shell and rotating therewith, and adapted to engage the heavier material thrown to the inner wall of the bowl and facilitate the progression thereof from one'end to the other.

2. In a. centrifugal separator, a rotary bowl flaring outwardly from the feed end and having a central opening at the discharge end and an inlet through said feed end, an inner shell having inwardly extending flanges at each end and a tubular mounting and radial extensions from said mounting to the shell adapted to, permit the inflow of the liquid through one end to the inner diameter or level of said opening in the head during rotation, a shaft supporting said bowl and extending through said tubular mounting, a deflector secured to the inner end of said shell mounting and opposing said inlet opening and adapted to direct the liquid to the inner wall surface of the bowl while increasing its linear velocity and coincidently retarding the speed of the shell, and means for driving said bowl.

3. In a centrifugal separator, a bowl having a central opening in the discharge end and an annular inlet at the feed end, an intake, means for driving said bowl connected to the source of material to be fed into the machine and having an annular chamber communicating with the bowl inlet, means for distributing and accelerating the inflowing liquid, means for regulating the depth of the liquid being treated, means introduced in the path ofthe discharge for supplementing the aforesaid driving means and for eecting an outlet, and means for skimming this lighter material at the discharge. i 4. In a centrifugal separator, a bowl close at one end and having an 'annular inlet and a central free opening at the other end, and annular discharge passages surrounding said free openin g and forming impinging surfaces meeting the outflow and adapted to maintain the momentum in the rotation of the bowl, a shaft carrying said bowl and means for driving said shaft. j

5. Ina centrifugal separator, a main shaft, a bowl having shaft bearings,an annular feed inletl at one end and a central discharge outlet at the other end, outlet passages from 'said discharge end, and pockets with relief openings through the side of the bowl, valves closing said openings, a valve gear connected with said valve, including valve stemsk and rocker arms, pivotally supported from said shaft, a cam slidably mounted onsaid vshaft having a pin extending inwardly therefrom in a slot in said shaft, and an operating rod introduced into said shaft and slidable therein and engaging said pin, and means for driving said casing. y

6. In a centrifugal separator, a main shaft, a bowl mounted on said shaft and suitably driven, .a shell contained within said bowl and supported from a tubular mounting having radial extensions and openings through said extensions, an axially adjustable journal member mounted on said shaft and supporting said tubular mounting of said shell, and having an annular flange therefrom engaging the mounting of said shell and bearing therefor, said bowl and said shell flaring outwardly from one end in parallel or nearly' parallel directions forming an incline in the direction of the discharge end, meansfor feeding liquid under pressure to the feed end, means 'for varying the speed of said shell in respect-to said bowl, and means for maintaining a con# stant speed in the rotation of said shell in relation to the speed of the bowl.

. 7 In centrifugal machines, a bowl suitably mounted and driven, an inner shell mounted to rotate at a different speed from the bowl,

and adjustable to regulate the depth of the liquid treated centrifugally, means for progressing subsided particles towards the outlet end of the bowl attached to said shell and means for adjusting the inner shell axially in varying the depth of said liquid. K,

8. In centrifugal machines, a conical bowl suitably driven, a. shaft mounted on said bowl, an inner conical .shell having a tubular mounting j ournalled on said shaft, a threaded sleeve screwed on to said shaft and forming a bearing and adjustable support for said tubular mounting, and lmeans of varying the distance between said shell and 'said bowl by moving the shell and its mounting axially.

9. In centrifugal machines, a bowl having a 'feed inlet member extending thereinto and a contracted discharge opening, a skimmer suitably distanced in relation to said discharge to remove the lightest effluent in the separationand formed of a plurality of spout like sections and means for driving said bowl.

10. In centrifugalmachines, a bowl suitably mounted; and'driven, an inner shell coaXially and rotably mounted in relation -to the bowl and having inwardly projecting flanges, one flange -at the-'outlet end having an inner di'- ameter less than the diameter of the outlet from thebowl a-nd-theother flange hav-ing a diameter greater than the outlet of the bowl and soformed as to permitliquid to enter said shell and carry an accumulation of lightV floatable impurities within said shell.

1l. In centrifugal machines, a bowl suitably mounted and driven, flexible scraper member over the surface of the bowl for facilitating the progression ofr subsided material along the bowl wall from one end to the other end, and outwardly recessed outlets from the bowl wall, at intervals circumferentially for relieving the bowl of the heaviermateri'al during rotation.V

13. In a centrifugal' separator, a rotary lbowl suitably mounted and driven and havingxvalve seats in a circular row surroundingv ports forming relief openings beyond the bowl periphery and adjacent to the outlet end, valves closing said relief openings, 'rod gears operatingsaid valves and means for'fpushing subsided material to reach said valves and ports.

14. Inl a centrifugal separator, a rotary bowl suitably mounted on a shaftand' driven,

an inner shell having a mounting independently journalled on said shaft andopen to the incoming `material at the top and bottom-suitably supported away Afrom the bowl inlet at the feed end, and a spiral spring scraper secured to each end of the shell and free therebetween for the progression of the material from one end to the discharge end in the bowl.

15. Ina centrifugal separator, a bowl having an inlet opening at one end, and a cover surrounding a central discharge, an

said valve, a slidable cam 4mounted on said` shaft suitably operated, connecting rods reciprocated and operatively associated with said cam and engaging said valves, and means for driving said casing.

1'?. In a centrifugal separator, a main shaft, a bowl suitably mounted and rotated, an adjustable inner shell within said bowl and spring Scrapers carried therewith, .a dish shaped deiiector secured to said shell at the end opposing the inlet into said bowl, vand having itswall extending in the direction n of the inner wall of said bowl, and means for driving said bowl.

l8.-In ycentrifugal separators, a bowl suitably mounted and driven and having an annular chamber and discharge pockets at intervals from said channel, a rotatory 'A scraper operatively mounted and rotating at a variable speed to the bowl and a drag link carried by the scrape-r mounting and gathering the subsided particles toward pockets.

19. `In centrifugal machines, a bowl suitably mounted on a driven shaft, an inner rotating shell adjustable lengthwise and turning on the bowl shaft and a dierential gear mechanism drivin'gthe shell at speeds variable to the bowl and in the same direction.

20. In centrifugal machines for the continuousy treatment of fluid mixtures of solids and liquids, a bowl suitably mountedfor rotation and driven, an inlet and an outlet for themain Huid stream and outlets for sinkable and floatable rejections, scraper means adapted to sweep sinkable rejections over the inner surface of the bowl to storage lWells in the wall of the bowl, outlet ports from said wells with closures, means to operate said closures intermittently during the rotation of the bowl for the intermittent ejection of sinkable particles through said ports and skim.- ming spout means for the continuous ejection of floatable rejects from the bowl.

21. In a machine for removing impurities from fibrous vegetable pulps in aqueous suspension, means for continuously feeding the raf pulp mixture into a revolving centrifugal separating bowl and thereby causing the mixture to revolve therewith at a speed sufficient to effect rapid subsidence of sinkable rejections and the rapid flotation of fioatable reject-ions, means for guiding the liow of the mixture within the bowl through a separating region, including a shallow frusto-conical member delivering an annular stream continuously, and removing floatable rejections from the bowl, means for intermittently removing sinkable rejections from the bowl during separations and means for continuously discharging the purified mixture from the bowl at a velocity less than its peripheral velocity within the separating regions.

22. In a centrifugal separator, a bowl rotatably mounted and forming an intermediary collecting member in the course of a Continuously flowing stream and having an annular or ring cover at the outlet and forming an open discharge and a central inlet at the other end, a shell of corresponding shape to the bowl independently rotated and forming therewith an annular settlement chamber and lighter liquid discharge, a spring scraper member attached to the shell and progressing the heavier material during the operation, means for driving the bowl and incidentally turning the shell, and valves recessed in the bowl wall adjacent to the outlet end and operated intermittently in relation to the continuous operation of the bowl.

23. In centrifugal machines, a main shaft, a bowl having an inlet at one end and an outlet at the other end and mounted on said shaft, an inner shell independently mounted on said shaft and longitudinally adjustable to vary the cubic contents of liquid treated in an annular chamber between the shell and the bowl according to selection and in agreement with the centrifugal action 0n the particular liquid substance treated and means for rotating said bowl and shell.

24:. In a centrifugal separator, a rotary bowl suitably mounted and driven and having an outstanding flange at the outlet and supporting a ring cover and forming an annular channel for the heavier substance and from the bed of said channel outlet nipples valve controlled and arranged at intervals throughout the length of said channel, a rod valve gear operated coincidently with the driving mechanism and intermittently opening said nipples, and an inner shell independently mounted and driven at a varying speed from said bowl and forming a separating chamber with the bowl wall and an inwardly extending discharge passage to the open end of the bowl for the lighter liquid substance. Y

25. In a centrifugal separator, a bowl suitably mounted and driven to rotate about a central axis, an inlet spout thereinto, a discharge outlet in one end, discharge ports in the periphery of the bowl, a flexible scraper strip spirally wound within the bowl and attached at its extremities to an inner mounting journalled to rotate independently of the bowl, said flexible scraper strip being free be? tween its points of attachment to the inner mounting and adapted to hug the inner surface of the bowl lby the action of centrifugal 

